In article ,
Silvan wrote:

Oh, routing it out is an inescapable fact of life. The hole has a rim all
the way around, and IIRC the wood around this rim can only be 5/32" thick
without pooching above the table. If I made an entire insert out of
material that thin I would expect serious rigidity problems.

5/32" oak or maple, supported entirely around the rim and accross a
small span is surprisingly ridgid; quite a bit more rigid then plywood
for example. Just a though to save you some effort...

Paul K